Summary

• save divergent stale controller transcripts into deterministic recovery branch sessions instead of dropping local-only turns or auto-merging unsafe JSONL histories
• add persistent transcript revision/CAS metadata (revision, content_digest, writer_id) so snapshot/rewrite saves only commit from the controller's recorded disk baseline, while listing/meta updates preserve those persistence fields
• add long-lived runtime leases with an in-process owner registry plus Unix flock / Windows LockFileEx lease files, and wire desktop tab build/rebind/close/recovery paths so one writable runtime owns a session path
• keep pure stale-prefix conflicts adopting the newer disk transcript, and surface recovery sessions in desktop tabs/project tree with recovery metadata, warning toast action, sidebar badge, and recovery banner

Refs #5783

Verification

• go test -count=1 ./internal/agent
• go test -count=1 ./internal/control ./internal/boot
• cd desktop && go test -count=1 .
• pnpm --dir desktop/frontend typecheck
• pnpm --dir desktop/frontend check:css
• pnpm --dir desktop/frontend exec tsx src/__tests__/project-tree-runtime.test.ts
• GOOS=windows GOARCH=amd64 go test -c ./internal/agent -o "<tmp>/agent.test.exe"
• GOOS=linux GOARCH=amd64 go test -c ./internal/agent -o "<tmp>/agent.test"
• git diff --check

Cache impact

Cache-impact: none; this changes session persistence/recovery, sidecar metadata, and desktop runtime ownership, not provider-visible prompts, model input shaping, tool schemas, or cache key behavior.
Cache-guard: go test -count=1 ./internal/agent; go test -count=1 ./internal/control ./internal/boot; cd desktop && go test -count=1 .; pnpm --dir desktop/frontend typecheck; pnpm --dir desktop/frontend check:css; pnpm --dir desktop/frontend exec tsx src/__tests__/project-tree-runtime.test.ts; GOOS=windows GOARCH=amd64 go test -c ./internal/agent -o "<tmp>/agent.test.exe"; GOOS=linux GOARCH=amd64 go test -c ./internal/agent -o "<tmp>/agent.test".
System-prompt-review: no provider-visible system prompt, memory prefix, output style, skill index, or tool schema behavior changes.